Field of the Invention
This invention relates to a nitramine composite propellant composition which is improved in its casting characteristics during the production of propellants and in its mechanical properties as a propellant.
Conventional composite propellants comprise as main components, solid oxidizers and binders which also act as fuels (hereinafter referred to as binder), and they contain the oxidizers in high ratios.
Recently, a composition of composite propellant containing a larger amount of the oxidizer as compared with conventional ones is desired because of a demand for a higher performance of the propellant.
However, in conventional composite propellants, an increased amount of the oxidizer causes an increase of the viscosity of the slurry which is a mixture of the binder and the oxidizer, with the result being that coating becomes impossible in producing the propellant and in an extreme case, it is not possible to effect the mixing of the binder and the oxidizer.
Although the propellant can be prepared, the adhesive characteristics of the binder and the oxidizing agent after the curing are spoiled and the characteristics such as mechanical strength and elongation are degraded with the result being that a dewetting of the binder occurs on the surface of the oxidizer under severe environmental conditions thereby to cause cracks in the propellant, which may result in a possibility of extraordinary combustion on ignition or burning.
Various class of additives have been proposed in order to improve such drawbacks.
It is known, for example, that the mechanical properties of the propellants are improved by using as the additives imines such as tris(2-methylaziridinyl)phosphine oxide (hereinafter referred to as MAPO) or alkanol amines such as diethanol amine and triethanol amine, which act as surface bonding agents, when the binders are of the polybutadiene series and the oxidizer is ammonium perchlorate (hereinafter referred to as AP) or the like.
The indication that the characteristics of propellant are improved means herein that the physical strengths of the propellant such as the tensile strength are high and the elongation is large and that the ratio of the elongation of the propellant at the maximum tensile strength to the elongation at the fracture point has a value near to one. The relation between the elongation at the maximum tensile strength and the elongation at the fracture point is not explained herein in detail but the values of the ratio which are near to one mean that the adhesion of the solid components and the binder layers are firm and that their relation approaches that of an ideal state.
In addition, it is known that the above stated imines also improve the fluidity characteristics because they act as pot life extenders.
On the other hand, additives which are effective to provide easy casting during production of the propellants and are effective to improve the propellant characteristics have not been found in the case of nitramine composite propellants in which the binders are of the polybutadiene series and the oxidizers are nitramines which propellants recently have attracted public attention as smokeless propellants of high specific thrust.
The mechanical properties of nitramine composite propellants are rather degraded by the addition of imines therein, which latter are effective when the oxidizer is AP, and the addition of alkanol amines therein extremely deteriorates the fluidity with the result being that it becomes very difficult to effect casting, although it improves the mechanical properties of the nitramine composite propellant.